It is known that ophthalmic lenses are subjected to various manufacturing steps in order to give them the prescribed ophthalmic properties.
Processes for manufacturing ophthalmic lenses are known that comprise a step of providing an unprocessed or semi-finished lens blank, i.e. a lens blank none of the faces or only one of the faces of which is what is referred to as finished (or in other words a face that defines a simple or complex optical surface).
These processes then comprise one or more steps of machining at least one face of the unprocessed lens blank, in order to obtain what is referred to as a finished face, defining the sought-after optical surface providing the (possibly complex) optical properties prescribed to the wearer of the ophthalmic lens.
The expression “one or more steps of machining” is here understood to mean steps of what are referred to as roughing, finishing and polishing (machining by surfacing).
The roughing step makes it possible, starting from an unprocessed or semi-finished lens blank, to give the face(s) of the lens blank which are referred to as unfinished its (their) thickness and surface radii of curvature, whereas the finishing (also called smoothing) step consists in fining the grain or even the precision of the radii of curvature of the faces obtained beforehand and allows the curved surface(s) generated to be prepared (smoothed) for the polishing step. This polishing step is a step of surfacing the roughed or smoothed curved surface(s), and makes it possible to make the ophthalmic lens transparent. The roughing and finishing steps are the steps that set the thickness of the final lens and the radii of curvature of the treated surface, independently of the thickness of the initial object and of its initial radii of curvature.
It will be noted that one type of complex optical surface, referred to as a “free-form surface” or “digital surface”, requires particularly precise machining, such a surface for example combining a torus and a progression. The machining of such a complex optical surface is carried out using at least one very high-precision machine tool at least for the roughing step, or even for the finishing and polishing step, and a polisher capable of polishing the surface(s) obtained in the preceding steps without deforming the ophthalmic lens.